How to fill 100% of remaining height?

Question

+--------------------+
|                    |
|                    |
|                    |
|                    |
|         1          |
|                    |
|            


        

Answer 1

I know this is an old question, but nowadays there is a super easy form to do that, which is CCS Grid, so let me put the divs as example:

<div id="full">
  <div id="header">Contents of 1</div>
  <div id="someid">Contents of 2</div>
</div>

then the CSS code:

.full{
  width:/*the width you need*/;
  height:/*the height you need*/;
  display:grid;
  grid-template-rows: minmax(100px,auto) 1fr;
 }

And that's it, the second row, scilicet, the someide, will take the rest of the height because of the property 1fr, and the first div will have a min of 100px and a max of whatever it requires.

I must say CSS has advanced a lot to make easier programmers lives.

Answer 2

    html,
    body {
        height: 100%;
    }

    .parent {
        display: flex;
        flex-flow:column;
        height: 100%;
        background: white;
    }

    .child-top {
        flex: 0 1 auto;
        background: pink;
    }

    .child-bottom {
        flex: 1 1 auto;
        background: green;
    }

    <div class="parent">
        <div class="child-top">
          This child has just a bit of content
        </div>
        <div class="child-bottom">
          And this one fills the rest
        </div>
    </div>